1. Field of the Invention
The present invention relates to a percussion power tool and, in particular to an electro-pneumatic hammer drill and/or chisel hammer that includes a motor located in the tool housing for driving the output member and a percussion mechanism. The percussion power tool further has a chuck for receiving a working tool displaceable along a longitudinal axis by the percussion mechanism, and a locking mechanism for releasably securing the chuck on the output member. The locking mechanism has at least one locking member which provides in its locking position for a formlocking connection between a connection member of the chuck and the output member. The locking member is displaceable in a radial, with respect to the longitudinal axis of the tool, direction into a release position in which the formlocking connection of the connection member of the chuck and the output member is lifted off, so that the chuck can be lifted off the output member. There is further provided an adjusting sleeve that prevents, in its blocking position, a radial displacement of the at least one locking member from the locking position thereof. The adjusting sleeve is displaceable against a biasing force into a release position in which the at least one locking member is displaceable into its release position.
2. Description of the Prior Art
In percussion power tools as described above, the chuck can be comfortably lifted off the tool, e.g., in order to be replaced by a new chuck or any other type of a working tool holder.
German Publication DE 34 43 186 A1 discloses a hand-held power tool having a sleeve-shaped output member in which a die is displaceable and on which a chuck is mounted. The tool further includes radially displaceable holding elements which provide for an axial formlocking connection between a connection member of the chuck and the output member. In their locking position, the holding elements are supported by an adjusting sleeve displaceable in a direction opposite the operational direction of the tool by a spring and toward a circlip. In order to lift the chuck off the output member, the adjusting sleeve is displaced in the operational direction against the biasing force of the spring so that the holding elements can be displaced radially outwardly, lifting off the formlocking connection between the chuck and the output member.
The drawback of the power tool described above consists in that during operation, in particular during an idle stroke, the die impacts an axial stop of the sleeve-shaped output member, and a very large portion of the impact energy is transmitted to the adjusting sleeve by the connection member and the circlip mounted thereon. The impact energy acting on the adjusting sleeve is often sufficient to displace the adjusting sleeve in the operational direction so far that the holding members can displace in their release position. This results in many cases in inadvertent falling of the chuck off of the power tool.
Accordingly, the object of the present invention is to provide a percussion power tool in which the drawback off the known power tool is eliminated and an inadvertent falling of the chuck off the tool is prevented.